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TDF8553J

I2C-bus controlled 4 X 50 Watt power amplifier and multiple voltage regulator

NXP Semiconductors. 

NXP Semiconductors

TDF8553J

4 × 50 Watt power amplifier and multiple voltage regulator

external pull-up resistor. If a failure occurs, pin DIAG remains LOW during the failure and

no clipping information is available. The microcontroller can read the failure information

via the I2C-bus.

8.5 Amplifiers

8.5.1 Muting

A hard mute and a soft mute can both be performed via the I2C-bus. A hard mute mutes

the amplifier within 0.5 ms. A soft mute mutes the amplifier within 20 ms and is less

audible. A hard mute is also activated if a voltage of 8 V is applied to pin STB.

8.5.2 Temperature protection

If the average junction temperature rises to a temperature value that has been set via the

I2C-bus, a thermal protection pre-warning is activated making pin DIAG LOW. If the

temperature continues to rise, all four channels will be muted to reduce the output power

(soft thermal clipping). The value at which the temperature mute control activates is fixed;

only the temperature at which the thermal protection pre-warning signal occurs can be

specified by bit D4 in instruction byte IB3. If implementing the temperature mute control

does not reduce the average junction temperature, all the power stages will be switched

off (muted) at the absolute maximum temperature Tj(max).

8.5.3 Offset detection

Offset detection can only be performed when there is no input signal to the amplifiers, for

instance when the external digital signal processor is muted after a start-up. The output

voltage of each channel is measured and compared with a reference voltage. If the output

voltage of a channel is greater than the reference voltage, bit D2 of the associated data

byte is set and read by the microcontroller during a read instruction. Note that the value of

this bit is only meaningful when there is no input signal and the amplifier is not muted.

Offset detection is always enabled.

8.5.4 Speaker protection

If one side of a speaker is connected to ground, a missing current protection is

implemented to prevent damage to the speaker. A fault condition is detected in a channel

when there is a mismatch between the power current in the high side and the power

current in the low side; during a fault condition the channel will be switched off.

The load status of each channel can be read via the I2C-bus: short to ground (one side of

the speaker connected to ground), short to VP (one side of the speaker connected to VP),

and shorted load.

8.5.5 Line driver mode

An amplifier can be used as a line driver by switching it to low gain mode. In normal mode,

the gain between single-ended input and differential output (across the load) is 26 dB. In

low-gain mode the gain between single-ended input and differential output is 20 dB.

TDF8553J_1

Objective data sheet

Rev. 01 — 3 December 2008

© NXP B.V. 2008. All rights reserved.

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